Lithium difluoro(oxalate)borate as an efficient and multifunctional additive for extended cycling life of LiFePO₄ cathodes

Reasonable design of cathode-electrolyte interface (CEI) with high electrochemical stability and high ionic conductivity is crucial for improving the electrochemical performance of cathode materials. Herein, lithium difluoro(oxalate)borate (LiDFOB) is used as an efficient electrolyte additive to form a robust, dense, and conductive CEI on LiFePO₄ cathode, which significantly enhances the rate capability and cycling stability. Specifically, the introduction of LiDFOB promotes the formation of a fluoride (F)- and boron (B)-rich CEI, effectively enhancing ion transport kinetics. Simultaneously, the generated CEI exhibits excellent stability, efficiently suppressing the continuous decomposition of the electrolyte and structural damage of LiFePO₄ cathode over prolonged cycling. Consequently, the LiFePO₄ cathode with LiDFOB additive exhibits a highly reversible capacity of 133.4 mAh g⁻¹ at 0.5 C and an excellent capacity retention of 94.4% over 400 cycles, which is superior to LiFePO₄ without additive (only 66.1% capacity retention). This work confirms the promising potential of LiDFOB as a multifunctional electrolyte additive and provides new insights for constructing high-performance CEI.